Prepared in cooperation with the City of Overland Park, Kansas

Flood-Inundation Maps for Indian Creek and 

Tomahawk Creek, Johnson County, Kansas, 2014

Scientific Investigations Report 2014–5202

U.S. Department of the Interior

U.S. Geological Survey

Flood-Inundation Maps for Indian Creek 

and Tomahawk Creek, Johnson County, 

Kansas, 2014

By Seth E. Studley and Arin J. Peters

Prepared in cooperation with the City of Overland Park, Kansas

Scientific Investigations Report 2014–5202

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Studley, S.E., and Peters, A.J., 2014, Flood-inundation maps for Indian Creek and Tomahawk Creek, Johnson County, 

Kansas, 2014: U.S. Geological Survey Scientific Investigations Report 2014–5202, 12 p., http://dx.doi.org/10.3133/

sir20145202.

ISSN: 2328-0328 (online)
iii

Acknowledgments

The authors wish to thank the many local, State, and Federal agencies that have cooperated 

in the funding for the operation and maintenance of the streamgages used for this study, 

especially the city of Overland Park, Kansas and Johnson County, Kansas. Special thanks are 

given to the National Weather Service for their continued support of the U.S. Geological Survey 

flood-inundation mapping initiative. 
iv

Contents

Abstract...........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Study Area Description........................................................................................................................3

Previous Studies ...................................................................................................................................7

Creation of Flood-Inundation-Map Library................................................................................................7

Computation of Water-Surface Profiles............................................................................................7

Hydrologic Data............................................................................................................................7

Topographic and Bathymetric Data..........................................................................................9

Hydraulic Structures ...................................................................................................................9

Energy-Loss Factors....................................................................................................................9

Hydraulic Model...........................................................................................................................9

Development of Water-Surface Profiles................................................................................10

Development of Flood-Inundation Maps ........................................................................................10

Flood-Inundation Map Delivery...............................................................................................10

Disclaimer for Flood-Inundation Maps .................................................................................11

Uncertainties and Limitations Regarding Use of Flood-Inundation Maps ......................11

Summary........................................................................................................................................................11

References Cited..........................................................................................................................................12

Figures

1. Map showing location of study reaches for Indian and Tomahawk Creeks in 

Johnson County, Kansas, and location of U.S. Geological Survey streamgages..............2

2. Screen capture showing flood-inundation map for the upper reach of Indian Creek 

corresponding to a stage of 22.00 feet at the U.S. Geological Survey streamgage 

(06893300).......................................................................................................................................4

3. Screen capture showing flood-inundation map for Tomahawk Creek corresponding 

to a stage of 22.00 feet at the U.S. Geological Survey streamgage (06893350)..................5

4. Screen capture showing flood-inundation map for the lower reach of Indian Creek 

corresponding to a tage of 33.00 feet at the U.S. Geological Survey streamgage 

(06893390).......................................................................................................................................6

Tables

1. Information for U.S. Geological Survey streamgages along Indian Creek and Tomahawk Creek in Johnson County, Kansas...................................................................................3

2. Peak discharges for selected annual exceedance probabilities on Indian and Tomahawk Creeks in Johnson County, Kansas.................................................................................7

3. Calibration of model to target stages, and observed and simulated water-surface 

elevations for the streamgage at Indian Creek at Overland Park, Kansas (station no. 

06893300) with corresponding discharges based on the most current stage-discharge 

relation (rating no. 48)..................................................................................................................8
v

4. Calibration of model to target stages, and observed and simulated water-surface 

elevations for the streamgage at Indian Creek at State Line Road, Leawood, Kansas 

(station no. 06893390) with corresponding discharges based on the most current 

stage-discharge relation (rating no. 4)......................................................................................8

5. Calibration of model to target stages, and observed and simulated water-surface 

elevations for the streamgage at Tomahawk Creek at Overland Park, Kansas (station no. 06893350, old site) with corresponding discharges based on the most current 

stage-discharge relation (rating no. 3)......................................................................................9

Conversion Factors

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2

) 2.590 square kilometer (km2)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Vertical coordinate information is referenced to (1) stage, or the height above an arbitrary 

datum established at a streamgage; and (2) altitude, or the height above the North American 

Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 

(NAD 83).

Abstract

Digital flood-inundation maps for a 6.4-mile upper reach 

of Indian Creek from College Boulevard to the confluence 

with Tomahawk Creek, a 3.9-mile reach of Tomahawk Creek 

from 127th Street to the confluence with Indian Creek, and a 

3.7-mile lower reach of Indian Creek from the confluence with 

Tomahawk Creek to the Kansas/Missouri border at State Line 

Road in Johnson County, Kansas, were created by the U.S. 

Geological Survey in cooperation with the city of Overland 

Park, Kansas. The flood-inundation maps, which can be 

accessed through the USGS Flood Inundation Mapping Science website at http://water.usgs.gov/osw/flood_inundation/, 

depict estimates of the areal extent and depth of flooding 

corresponding to selected water levels (stages) at the U.S. 

Geological Survey streamgages on Indian Creek at Overland 

Park, Kansas (06893300), Indian Creek at State Line Road, 

Leawood, Kansas (06893390), and Tomahawk Creek near 

Overland Park, Kansas (06893350). Near real time stages at 

this streamgage may be obtained on the Web from the U.S. 

Geological Survey National Water Information System at 

http://waterdata.usgs.gov/ or the National Weather Service 

Advanced Hydrologic Prediction Service at http://water.

weather.gov/ahps/, which also forecasts flood hydrographs at 

these sites. 

Flood profiles were computed for the stream reaches 

by means of a one-dimensional step-backwater model. The 

model was calibrated for each reach by using the most current 

stage-discharge relations at the Indian Creek at Overland Park, 

Kansas; Indian Creek at State Line Road, Leawood, Kansas; 

and Tomahawk Creek at Overland Park, Kansas, streamgages. 

The hydraulic models were then used to determine 15

water-surface profiles for Indian Creek at Overland Park, Kansas; 17 water-surface profiles for Indian Creek at State Line 

Road, Leawood, Kansas; and 15 water-surface profiles for 

Tomahawk Creek at Overland Park, Kansas, for flood stages at 

1-foot intervals referenced to the streamgage datum and ranging from bankfull to approximately the next interval above 

the 0.2 percent annual exceedance probability flood level. 

The simulated water-surface profiles were then combined 

in a geographic information system with a digital elevation 

model derived from light detection and ranging data (having 

a 0.429-foot vertical and 0.228-foot horizontal resolution) to 

delineate the area flooded at each water level. 

The availability of these maps, along with Web information regarding current stage from the U.S. Geological Survey 

streamgage and forecasted high-flow stages from the National 

Weather Service, will provide emergency management personnel and residents with information that is critical for flood 

response activities such as evacuations and road closures, as 

well as for postflood recovery efforts.

Introduction 

The adjacent communities of Overland Park and 

Leawood, Kansas (fig. 1), together form a large urban community with a total estimated population of 205,239 (U.S. Bureau 

of Census, 2010). Overland Park (fig. 1) has had moderate 

flooding events numerous times most notably in 1984, 1990, 

and 1998 (U.S. Geological Survey, 2014a). 

Overland Park officials relied on several information 

sources, all of which are available on the Web, to make 

decisions on how to best alert the public and mitigate flood 

damages. One source is the Federal Emergency Management 

Agency (FEMA) flood insurance study (FIS) for Johnson 

County, Kansas (fig. 1), and incorporated areas dated August 

3, 2009 (Federal Emergency Management Agency, 2009). 

A second source of information is U.S. Geological Survey 

(USGS) streamgages on Indian Creek at Overland Park, Kansas (06893300); Indian Creek at State Line Road, Leawood, 

Kansas (06893390); and on Tomahawk Creek near Overland Park, Kansas (06893350; fig. 1), from which current or 

historical water levels (stage) can be obtained (U.S. Geological Survey, 2014a). A third source is the National Weather 

Service (NWS) forecast of peak stage at the USGS Tomahawk 

Creek near Overland Park streamgage through the Advanced 

Hydrologic Prediction Service (AHPS) site (National Weather 

Service, 2014). 

Although the current stage at a USGS streamgage is 

particularly useful for residents in the immediate vicinity of a 

streamgage, it is of limited use to residents farther upstream or 

downstream because the water-surface altitude is not constant 

along the entire stream reach. Knowledge of water level at a 

streamgage is difficult to translate into depth and areal extent 

of flooding at points distant from the streamgage. To address 

these informational gaps, the USGS, in cooperation with the 

Flood-Inundation Maps for Indian Creek and Tomahawk 

Creek, Johnson County, Kansas, 2014

By Seth E. Studley and Arin J. Peters 
2 Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014

Figure 1. Location of study reaches for Indian and Tomahawk Creeks in Johnson County, Kansas, and location 

of U.S. Geological Survey streamgages.

#

#

#

#

Prairie

Village

Leawood

Overland

Park

§ ̈¦435

J am es B ranch

Tom ahaw k Cr e e k

I n di an Cree k

Johnson

Jackson County

County KANSAS

MISSOURI

¬«150

£¤69

£¤169

£¤169

06893300

06893350

06893390

06893350

original

M

State Line Rd

Roe Avenue Roe Avenue

ISSION RD

W 119TH ST

COLLEGE BLVD

W 127TH ST

Kansas Missouri

Map area Impervious surface

Tomahawk Creek reach

Lower Indian Creek reach

Upper Indian Creek reach

U.S. Geological Survey streamgaging 

 station and Identifier

06893350

EXPLANATION

0 0.5 1 1.5 MILES

0

Base map from U.S. Geological Survey digital data, 2012, 1:24,000

Albers Conic Equal -Area projection

Standard parallels 20°30’N

Central meridian 96°W

Land cover from 2013 Mid-American 

Regional Council’s (MARC) Natural 

10.5 1.5 KILOMETERS Resources Inventory (NRI) layer

#

94°40’

38°55’

N

Leawood
Introduction 3

city of Overland Park, Kansas, produced a library of floodinundation maps that are referenced to the stages recorded 

at USGS streamgages on Indian and Tomahawk Creeks. 

By referring to the appropriate map, emergency responders can discern the severity of flooding (depth of water and 

areal extent), identify roads that are or will soon be flooded, 

and make plans for notification or evacuation of residents in 

potential danger for some distance upstream and downstream 

from the streamgage. In addition, the capability to visualize 

the potential extent of flooding has been shown to motivate 

residents to take precautions and heed warnings that they previously might have disregarded. 

Purpose and Scope

This report describes the development of a series of 

estimated flood-inundation maps for Indian and Tomahawk 

Creeks at Leawood and Overland Park, Kansas (fig. 1), and 

identifies where on the Web the maps can be located and 

ancillary data (Geographic Information System [GIS] flood 

polygons and depth grids) can be downloaded. 

The scope of the study was limited to a 6.4-mile upper 

reach of Indian Creek from College Boulevard to the confluence with Tomahawk Creek, a 3.9-mile reach of Tomahawk 

Creek from 127th Street to the confluence with Indian Creek, 

and a 3.7-mile lower reach of Indian Creek from the confluence with Tomahawk Creek and the Kansas/Missouri border at 

State Line Road in Johnson County, Kansas (fig. 1).

The maps were produced for flood levels referenced to 

the stage recorded at three USGS streamgages. Indian Creek at 

Overland Park, Kansas (06893300), is located within the upper 

reach of Indian Creek (fig. 1). Tomahawk Creek near Overland 

Park, Kansas (06893350), is located in the upper half of the 

Tomahawk Creek reach (fig. 1). Indian Creek at State Line 

Road, Leawood, Kansas (06893390), is located at the end of 

the lower reach of Indian Creek (fig. 1). 

The maps cover a range in stage from 8 to 22 feet (ft; 

gage datum) at Indian Creek at Overland Park, 10 to 23 ft at 

Tomahawk Creek at Overland Park, and 17 to 33 ft at Indian 

Creek at State Line Road, Leawood (figs. 2–4). The lower 

stage at each site represents approximately bankfull and the 

upper stage exceeds the stage that corresponds to the estimated 

0.2-percent annual exceedance probability flood (500-year 

recurrence interval flood).

Methods used are generally cited from previously 

published reports. If techniques differed substantially from 

previously documented methods because of local hydrologic 

conditions or availability of data, they are described in detail 

in this report. Maps were produced for water levels referenced 

to the stage at each of the streamgages and range from approximately bankfull to the stage corresponding to the 0.2-percent 

annual exceedance probability flow.

Study Area Description

Indian Creek and Tomahawk Creek are in northeast 

Kansas in the Osage Questas (Omernik, 1987). The drainage 

areas from the creeks range from 20.5 square miles (mi2) at 

the Tomahawk Creek near Overland Park, Kansas, gage to 

64.2 mi2 at the downstream extent of the study reach (table 1). 

The headwaters originate in Johnson County, Kansas, and the 

streams flow generally northeast (fig. 1). No primary tributaries to Indian Creek join the main stem as it flows through 

Overland Park until Tomahawk Creek joins it near the Kansas/

Missouri border (fig. 1). The study reaches are approximately 

6.4 mi long for the upper reach of Indian Creek, 3.9 mi long 

for Tomahawk Creek, and 3.7 mi long for the lower reach of 

Indian Creek from Tomahawk Creek to the Kansas/Missouri 

border (fig. 1) and have an average top-of-bank channel width 

of 70–85 ft and an average channel slope of 11 feet per mile 

(ft/mi) (described in the Topographic and Bathymetric Data 

section). All of the land contiguous to the study reaches is 

classified as urban or developed (Fry and others, 2011). The 

main channels within the study reaches have 23 primary road 

crossings and 10 other structures (foot bridges and cart paths) 

that lie within the channel or the adjacent flood plain.

Table 1. Information for U.S. Geological Survey streamgages along Indian Creek and Tomahawk Creek in Johnson County, KS.

[mi2, square miles; ft, feet; ft3/s, cubic feet per second]

Station name and 

location (fig. 1)

Station 

number

Drainage 

area (mi2

) Latitude Longitude Period of peakflow record

Maximum 

recorded 

stage (ft) and 

date

Maximum 

discharge 

(ft3

/s) and date

Indian Creek at Overland 

Park, Kansas 06893300 26.6 38°56′26′′ 94°40′16′′ Mar. 7, 1963, to present

17.78, June 9, 

1984

12,800, June 9, 

1984

Tomahawk Creek near 

Overland Park, Kansas 06893350 20.5

38°54′23′′ 

(new 

location)

94°38′24′′ 

(new 

location)

1970–1982 

and 2011 to 

present

19.17, Aug. 

13, 1982

8,250, Aug. 

13, 1982

Indian Creek at State Line 

Road, Leawood, Kansas

06893390 64.17 38°56′18′′ 94°36′28′′ Mar. 22, 2003, 

to present

25.50, June 

14, 2010

18,700, June 

14, 2010
4 Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014

0 1 MILES

0 1 KILOMETERS

N

g02

Figure 2. Flood-inundation map for the upper reach of Indian Creek corresponding to a stage of 22.00 feet at the U.S. Geological Survey streamgage (06893300).
Introduction 

5

Figure 3. Flood-inundation map for Tomahawk Creek corresponding to a stage of 22.00 feet at the U.S. Geological Survey streamgage (06893350).

N

0 1 MILES

0 1 KILOMETERS

g03
6 Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014

N

0 1,000 1,500 500 2,000 FEET

0 500 METERS 250

g04

Figure 4. Flood-inundation map for the lower reach of Indian Creek corresponding to a stage of 33.00 feet at the U.S. Geological Survey streamgage (06893390).
Creation of Flood-Inundation-Map Library 7

Previous Studies

The current FIS for Indian Creek in Johnson County, 

Kansas (Federal Emergency Management Agency, 2009), was 

completed by Phelps Engineering Inc. in 2006. The current 

FIS for Tomahawk Creek in Johnson County, Kansas (Federal Emergency Management Agency, 2009), was completed 

by Phelps Engineering, Inc. in 1998. Those studies provided 

information on the 1.0- and 0.2-percent annual exceedance 

probability water-surface profiles and associated flood plain 

(table 2). Estimates of the peak discharges for the 10-, 2.0-, 

1.0-, and 0.2-percent annual exceedance probability flood 

along Indian Creek and Tomahawk Creek, as listed in table 2, 

are described by (Federal Emergency Management Agency, 

2009). 

Creation of Flood-Inundation-Map 

Library

The USGS has standardized the procedures for creating 

flood-inundation maps for flood-prone communities (U.S. 

Geological Survey, 2014b) so that the process followed and 

products produced are similar regardless of which USGS 

office is responsible for the work. 

Tasks specific to development of the maps were (1) relocation of one streamgage on Tomahawk Creek in 2014

(fig. 1); (2) collection of topographic data and geometric 

data (for structures/bridges) throughout the study reach; 

(3) determination of energy-loss factors (roughness coefficients) in the stream channel and flood plain, and compilation 

of steady-flow data; (4) computation of water-surface profiles 

by use of the U.S. Army Corps of Engineers HEC–RAS 

hydraulic model (U.S. Army Corps of Engineers, 2010); 

(5) production of estimated flood-inundation maps at incremental stream stages by use of the U.S. Army Corps of Engineer’s HEC–GeoRas computer program (U.S. Army Corps of 

Engineers, 2009) and a GIS; and (6) development of a Web 

interface that links to USGS real-time streamgage information and NWS forecasted peak stage to facilitate the display of 

user-selected flood-inundation maps on the Web.

Computation of Water-Surface Profiles

The water-surface profiles used to produce the 46 floodinundation maps (15 for the upper reach of Indian Creek, 

14 for the Tomahawk Creek reach, and 17 for the lower reach 

of Indian Creek; fig. 1) in this study were computed by using 

HEC–RAS version 4.1.0 (U.S. Army Corps of Engineers, 

2010). HEC–RAS is a one-dimensional step-backwater model 

for simulation of water-surface profiles with gradually varied, 

steady-state (or unsteady-state) flow computation options.

Hydrologic Data

The study reaches include three streamgages (fig. 1). Two 

of the gages were already in operation (Indian Creek at Overland Park, Kansas [06893300] and Indian Creek at State Line 

Road, Leawood, Kansas [06893390]; fig. 1), and one gage 

(Tomahawk Creek near Overland Park, Kansas [06893350]; 

fig. 1) was moved 0.75 mi upstream from its original location, 

at the cooperator’s request, on April 10, 2014. Stage is measured every 15 minutes, transmitted hourly by a satellite radio 

in the streamgage, and made available on the Web through 

the USGS National Water Information System (NWIS; U.S. 

Geological Survey, 2014). Stage data from these streamgages 

are referenced to a local datum, but can be converted to 

water-surface altitudes referenced to the North American 

Vertical Datum of 1988 (NAVD 88) by adding 857.26 ft 

for 06893300, 803.43 ft for 06893390, and 844.33 ft for 

06893350 (fig. 1). Continuous records of streamflow are computed from a stage-discharge relation, which has been developed for the streamgage, and are available through the USGS 

NWIS website (U.S. Geological Survey, 2014a). The data 

from these three sites were used to calibrate the models. The 

flood-inundation maps developed for the Tomahawk Creek at 

Overland Park site that is now located on Roe Avenue used a 

simulated stage-discharge relation resulting from the calibration with the stage-discharge relation developed at the original 

gage location on 119th Street.

The rated discharges used in the model simulations 

(tables 3–5) were taken from the current stage-discharge relation at each stream gage and correspond to the target stages. 

Table 2. Peak discharges for selected annual exceedance probabilities on Indian and Tomahawk Creeks in Johnson County, Kansas.

 [mi2, square miles; ft3/s, cubic feet per second; Data from Federal Emergency Management Agency, 2009.]

Station name and location 

(station number, fig. 1)

Drainage 

area (mi2

)

Peak discharges (ft3

/s) for indicated annual exceedance probabilities 

(in percent)

10 2 1 0.2

Indian Creek at Overland Park, 

Kansas (06893300) 26.6 9,175 14,662 17,303 23,350

Tomahawk Creek near Overland 

Park, Kansas (06893350) 20.5 8,380 11,895 13,425 17,145

Indian Creek at State Line Road, 

Leawood, Kansas (06893390)

64.17 18,206 26,518 30,753 41,210
8 Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014

Table 3. Calibration of model to target stages, and observed and simulated water-surface elevations for the streamgage at Indian 

Creek at Overland Park, Kansas (station no. 06893300) with corresponding discharges based on the most current stage-discharge 

relation (rating no. 48).

[ft3/s, cubic feet per second; NAVD 88, North American Vertical Datum of 1988; ft, feet. Flood-inundation maps available online at http://pubs.usgs.gov/

sir/2014/5202]

Model calibration results 

Rated discharge

(ft3

/s)

Observed elevation

(NAVD 88)

Simulated elevation

(NAVD 88)

Rated stage

(ft)

Simulated stage

(ft)

Difference from 

rating

616 865.26 865.62 8 8.36 0.36

1,140 866.26 866.37 9 9.11 0.11

1,820 867.26 867.51 10 10.25 0.25

2,670 868.26 868.64 11 11.38 0.38

3,690 869.26 869.71 12 12.45 0.45

4,880 870.26 870.63 13 13.37 0.37

6,240 871.26 871.52 14 14.26 0.26

7,780 872.26 872.49 15 15.23 0.23

9,500 873.26 873.44 16 16.18 0.18

11,400 874.26 874.47 17 17.21 0.21

13,500 875.26 875.34 18 18.08 0.08

15,700 876.26 876.26 19 19.00 0

18,200 877.26 877.26 20 20.00 0

20,800 878.26 878.21 21 20.95 -0.05

23,600 879.26 879.22 22 21.96 -0.04

Table 4. Calibration of model to target stages, and observed and simulated water-surface elevations for the streamgage at Indian 

Creek at State Line Road, Leawood, Kansas (station no. 06893390) with corresponding discharges based on the most current stagedischarge relation (rating no. 4).

[ft3/s, cubic feet per second; NAVD 88, North American Vertical Datum of 1988; ft, feet. Flood-inundation maps available online at http://pubs.usgs.gov/

sir/2014/5202]

Model calibration results 

Rated discharge

(ft3

/s)

Observed elevation

(NAVD 88)

Simulated elevation

(NAVD 88)

Rated stage

(ft)

Simulated stage

(ft)

Difference from 

rating

3,300 820.43 820.88 17.00 17.45 0.45

4,120 821.43 821.71 18.00 18.28 0.28

5,060 822.43 822.56 19.00 19.13 0.13

6,120 823.43 823.44 20.00 20.01 0.01

7,430 824.43 824.37 21.00 20.94 0.06

9,120 825.43 825.33 22.00 21.90 -0.10

11,000 826.43 826.30 23.00 22.87 -0.13

13,200 827.43 827.33 24.00 23.90 -0.10

15,500 828.43 828.32 25.00 24.89 -0.11

18,100 829.43 829.36 26.00 25.93 -0.07

20,900 830.43 830.37 27.00 26.94 -0.06

23,900 831.43 831.34 28.00 27.91 -0.09

27,200 832.43 832.32 29.00 28.89 -0.11

30,800 833.43 833.37 30.00 29.94 -0.06

34,600 834.43 834.34 31.00 30.91 -0.09

38,700 835.43 835.45 32.00 32.02 0.02

43,000 836.43 836.43 33.00 33.00 0
Creation of Flood-Inundation-Map Library 9

No primary tributaries join Indian and Tomahawk Creeks 

within the study reaches (fig. 1); therefore, the gage-derived 

discharges were not adjusted for tributary inflows, but were 

held constant throughout the study reach for a given profile.

Topographic and Bathymetric Data

All topographic data used in this study are referenced 

vertically to NAVD 88 and horizontally to the North American 

Datum of 1983 (NAD 83). Cross-section altitude data and 

average channel slope were obtained from a digital elevation model (DEM) that was derived from light detection and 

ranging (lidar) data that were collected during December 

2011 by M.J. Harden Associates. Postprocessing of these data 

was completed by M.J. Harden Associates in April 2012. The 

original lidar data have a horizontal resolution of 0.228 ft and 

vertical accuracy of 0.429 ft at a 95percent confidence level 

for the open terrain land-cover category (root mean squared 

error of 0.410 ft). 

Where possible, DEM-generated cross sections were 

made to coincide with the locations of the within-channel 

field-surveyed cross sections. In these cases, within-channel 

data were directly merged with the DEM data. For all other 

cross sections, the within-channel data were estimated by 

interpolation from the closest field-surveyed cross section. 

Hydraulic Structures

Various structures consisting of bridges, culverts, roadway embankments, levees, and dams have the potential to 

affect water-surface altitudes during floods along the stream. 

Bridge-geometry data were obtained from field surveys completed by personnel from the USGS Kansas Water Science 

Center. 

Energy-Loss Factors

Hydraulic analyses require the estimation of energy 

losses that result from frictional resistance exerted by a channel on flow. These energy losses are quantified by the Manning’s roughness coefficient (n value). Field observations and 

high-resolution aerial photographs were used to select initial 

(precalibration) Manning’s roughness coefficients (n values) 

for energy-loss (friction-loss) calculations.

As part of the calibration process, the initial n values were varied by flow, and adjusted until the differences 

between simulated and observed water-surface altitudes at the 

streamgage were minimized. The final n values ranged from 

0.020 to 0.045 for the main channel and 0.015 to 0.15 for the 

overbank areas modeled in this analysis.

Hydraulic Model

The HEC–RAS analysis for this study was done by 

using the steady-state flow computation option. Steady-state 

flow data consisted of flow regime, boundary conditions, and 

rated discharges that produced water-surface altitudes at the 

streamgage cross section that matched target water-surface 

altitudes. These target water-surface altitudes coincided with 

even 1ft increments of stage referenced to the local gage 

Table 5. Calibration of model to target stages, and observed and simulated water-surface elevations for the streamgage at 

Tomahawk Creek at Overland Park, Kansas (station no. 06893350, old site) with corresponding discharges based on the most current 

stage-discharge relation (rating no. 3).

[ft3/s, cubic feet per second; NAVD 88, North American Vertical Datum of 1988; ft, feet. flood-inundation maps available online at http://pubs.usgs.gov/

sir/2014/5202]

Model calibration results 

Rated discharge

(ft3

/s)

Observed elevation 

(NAVD 88)

Simulated elevation

(NAVD 88)

Rated stage

(ft)

Simulated stage

(ft)

Difference from 

rating

2,490 854.33 854.82 10.00 10.49 0.49

3,060 855.33 855.64 11.00 11.31 0.31

3,670 856.33 856.43 12.00 12.10 0.10

4,360 857.33 857.24 13.00 12.91 -0.09

5,150 858.33 858.11 14.00 13.78 -0.22

6,000 859.33 858.99 15.00 14.66 -0.34

6,990 860.33 859.97 16.00 15.64 -0.36

8,290 861.33 861.20 17.00 16.87 -0.13

9,720 862.33 862.64 18.00 18.31 0.31

11,400 863.33 863.70 19.00 19.37 0.37

13,600 864.33 864.34 20.00 20.01 0.01

16,100 865.33 865.26 21.00 20.93 -0.07

18,900 866.33 866.23 22.00 21.90 -0.10

22,000 867.33 867.46 23.00 23.13 0.13
10 Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014

datum. Subcritical (tranquil) flow regime was assumed for the 

simulations. Normal-depth boundary conditions were assumed 

by using a friction slope estimated from the average streambed 

slope through the reach unless miscellaneous discharge measurements referenced to a known datum were available. The 

rated discharges that were used in the model were discussed in 

the section, “Hydrologic Data.”

The HEC-RAS model was calibrated to the current 

stage-discharge relation at each of the three streamgages. 

Model calibration was accomplished by adjusting Manning’s n

values and, in some cases, adding ineffective flow areas until 

the results of the hydraulic computations closely agreed with 

the observed water-surface altitudes for the rated discharges. 

Differences between observed and simulated water-surface 

altitudes for the 46 simulated flows at the USGS streamgage 

were equal to or less than 0.50 ft (tables 3–5). The results 

demonstrate that the model is capable of simulating accurate 

water levels over a wide range of flows in the basin.

Development of Water-Surface Profiles

The calibrated hydraulic model was used to generate 

water-surface profiles for three reaches on Indian and Tomahawk Creeks in Johnson County, Kansas, referenced to the 

most current stage-discharge relation at a gage within each 

reach (fig. 1). A total of 15 profiles were generated at 1-ft 

intervals between 8 ft and 22 ft as referenced to rating number 

48 at Indian Creek at Overland Park, Kansas (06893300; table 

3; fig. 1). These stages correspond to altitudes of 865.26 ft and 

879.26 ft NAVD 88, respectively (table 3). A total of 14 profiles were generated at 1-ft intervals between 10 ft and 23 ft as 

referenced to rating number 4 at Tomahawk Creek near Overland Park, Kansas (06893350; table 5; fig. 1). These stages 

correspond to altitudes of 854.33 ft and 867.33 ft NAVD 88, 

respectively (table 5). A total of 17 profiles were generated at 

1-ft intervals between 17 ft and 33 ft as referenced to rating number 4 at Indian Creek at State Line Road, Leawood, 

Kansas (06893390; table 4; fig. 1). These stages correspond 

to altitudes of 820.43 ft and 836.43 ft NAVD 88, respectively 

(table 4). 

Development of Flood-Inundation Maps

Flood-inundation maps were created for three of the 

USGS streamgages (figs. 2–4); all of which have been designated as NWS flood-forecast points. The maps were created 

in a GIS by combining the water-surface profiles and DEM 

data. The DEM data were derived from the same lidar data 

described previously in the section “Topographic and Bathymetric Data” and therefore have an estimated vertical accuracy 

of 2 ft (plus or minus 1 ft), which is based on rounding the 

computed vertical accuracy of the lidar data (plus or minus 

about 0.4 ft) to the nearest foot. Estimated flood-inundation 

boundaries for each simulated profile were developed with 

HEC–GeoRAS software (U.S. Army Corps of Engineers, 

2009), which allows the preparation of geometric data for 

import into HEC–RAS and processes simulation results 

exported from HEC—RAS (U.S. Army Corps of Engineers, 

2010). HEC–GeoRAS is a set of procedures, tools, and 

utilities for processing geospatial data in ArcGIS by using a 

graphical user interface (Whitehead and Ostheimer, 2009). 

Shapefile polygons and depth grids of the inundated areas 

for each profile were modified, as required, in the ArcMap 

application of ArcGIS (Esri, 2013) to ensure a hydraulically 

reasonable transition of the flood boundaries between modeled 

cross sections. 

Any inundated areas that were detached from the main 

channel were examined to identify subsurface connections, 

such as through culverts under roadways, with the main 

streams. Where such connections existed, the mapped inundated areas were retained in their respective flood maps; 

otherwise, the erroneously delineated parts of the flood extent 

were deleted. The flood-inundation areas are overlaid on 

high-resolution, georeferenced, aerial photographs of the study 

area. Bridge surfaces are displayed as inundated regardless 

of the actual water-surface altitude in relation to the lowest 

structural chord of the bridge or the bridge deck. Estimates of 

water depth can be obtained from the depth-grid data that are 

included with the presentation of the flood maps on an interactive USGS mapping application described in the following 

section, “Flood-Inundation Map Delivery.” The flood maps 

corresponding to the highest simulated water-surface profiles 

at each streamgage are presented in figures 2–4.

Flood-Inundation Map Delivery

The flood-inundation maps (figs. 2–4) and current study 

documentation are available online at the USGS Publications 

Warehouse (http://pubs.usgs.gov/sir/2014/5202). Also, a floodinundation mapping science website has been established at 

http://water.usgs.gov/osw/flood_inundation/ to provide a portal 

for USGS flood-inundation study information to the public.

That website has a link to interactive online map libraries that 

can be downloaded in several commonly used electronic file 

formats. At the map library site, each stream reach displayed 

contains further links to NWISWeb graphs of the current stage 

and streamflow at USGS streamgages 06893300, 06893350, 

and 06893390 (fig. 1) to which the inundation maps are referenced. A link also is provided to the NWS AHPS site (http:/

water.weather.gov/ahps/) so that the user can obtain applicable information on forecasted peak stage if applicable. The 

estimated flood-inundation maps are displayed in sufficient 

detail to note the extent of flooding with respect to individual 

structures so that preparations for flooding and decisions for 

emergency response can be completed efficiently. Depending on the flood magnitude, roadways are shown as shaded 

(inundated and likely impassable) or not shaded (dry and 

passable) to facilitate emergency planning and use. A shaded 

building should not be interpreted to mean that the structure is 

completely submerged; it means that bare-earth surfaces in the 

vicinity of the building are inundated. 
Summary 11

In these instances, the water depth (as indicated in the mapping application by holding the cursor over an inundated area) 

near the building would be an estimate of the water level 

inside the structure unless flood-proofing measures had been 

implemented.

Disclaimer for Flood-Inundation Maps 

The flood-inundation maps (figs. 2–4) should not be used 

for navigation, regulatory, permitting, or other legal purposes. 

The USGS provides these maps for a quick reference, emergency planning tool, but assumes no legal liability or responsibility resulting from the use of this information.

Uncertainties and Limitations Regarding Use of 

Flood-Inundation Maps 

Although the flood-inundation maps (figs. 2–4) represent the boundaries of inundated areas with a distinct line, 

some uncertainty is associated with these maps. The flood 

boundaries shown were estimated based on water stages and 

streamflows at selected USGS streamgages. Water-surface 

altitudes along the stream reaches were estimated by steadystate hydraulic modeling, assuming unobstructed flow, and 

using streamflows and hydrologic conditions anticipated at 

the USGS streamgages. The hydraulic model reflects the 

land-cover characteristics and any bridge, dam, levee, or other 

hydraulic structures existing as of December 2011. Unique 

meteorological factors (timing and distribution of precipitation) may cause actual streamflows along the modeled reach 

to differ from those assumed during a flood, which may lead 

to deviations in the water-surface altitudes and inundation 

boundaries shown. Additional areas may be flooded because 

of unanticipated conditions such as changes in the streambed 

altitude or roughness, backwater into primary tributaries along 

a main stem river, or backwater from localized debris or ice 

jams. The accuracy of the floodwater extent portrayed on these 

maps will differ with the accuracy of the digital elevation 

model used to simulate the land surface. 

If this series of flood-inundation maps will be used in 

conjunction with NWS river forecasts, the user should be 

aware of additional uncertainties that may be inherent or factored into NWS forecast procedures. The NWS uses forecast 

models to estimate the quantity and timing of water flowing 

through selected stream reaches in the United States. These 

forecast models (1) estimate the amount of runoff generated 

by precipitation and snowmelt, (2) simulate the movement of 

floodwater as it proceeds downstream, and (3) predict the flow 

and stage (and water-surface altitude) for the stream at a given 

location (AHPS forecast point) throughout the forecast period 

(every 6 hours and 3 to 5 days out in many locations). For 

more information on AHPS forecasts, please see http://water.

weather.gov/ahps/pcpn_and_river_forecasting.pdf.

Summary

A series of 46 digital flood-inundation maps were developed in cooperation with the city of Overland Park, Kansas, 

for two reaches on Indian Creek from College Boulevard to 

the Kansas/Missouri State Line and one reach on Tomahawk 

Creek from 127th Street to its confluence with Indian Creek 

totaling 14.0 miles. The maps were developed by using the 

U.S. Army Corps of Engineers’ HEC–RAS and HEC–GeoRAS programs to compute water-surface profiles, and to 

delineate estimated flood-inundation areas and depths of 

flooding for selected stream stages. The HEC–RAS hydraulic 

model was calibrated to the current stage-discharge relation 

at Indian Creek at Overland Park, Kansas (06893300), Indian 

Creek at State Line Road, Leawood, Kansas (06893390), 

Tomahawk Creek at Overland Park, Kansas (06893350), and 

National Weather Service flood-stage forecasts. For Indian 

Creek at Overland Park (06893300), the model was used to 

compute 15 water-surface profiles for flood stages at 1-foot 

(ft) intervals referenced to the streamgage datum and ranged 

from 8 ft or near bankfull to 22 ft, which exceeds the stage of 

the maximum recorded peak discharge. For Indian Creek at 

State Line Road (06893390), the model was used to compute 

17 water-surface profiles for flood stages at 1-ft intervals referenced to the streamgage datum and ranged from 17 ft or near 

bankfull to 33 ft, which exceeds the stage of the maximum 

recorded peak discharge. For Tomahawk Creek at Overland 

Park (06893300), the model was used to compute 14 watersurface profiles for flood stages at 1-ft intervals referenced to 

the streamgage datum and ranged from 10 ft or near bankfull 

to 23 ft, which exceeds the stage of the maximum recorded 

peak discharge. The simulated water-surface profiles were then 

combined in a Geographic Information System with a digital 

elevation model derived from light detection and ranging data 

to delineate estimated flood-inundation areas as shapefile polygons and depth grids for each profile. These flood-inundation 

polygons were overlaid on high-resolution, georeferenced 

aerial photographs of the study area. The flood maps are available through a mapping application that can be accessed on the 

U.S. Geological Survey Flood-Inundation Mapping Science 

website (http://water.usgs.gov/osw/flood_inundation).

Interactive use of the maps on this mapping application 

can give users a general indication of depth of water at any 

point by using the mouse cursor to click within the shaded 

areas. These maps, in conjunction with real-time stage data 

from the U.S. Geological Survey streamgages used in this 

analysis, and forecasted flood stage data from the National 

Weather Service Advanced Hydrologic Prediction Service will 

help to guide the general public in taking individual safety precautions, and will provide emergency management personnel 

with a tool to efficiently manage emergency flood operations 

and postflood recovery efforts.
12 Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014

References Cited

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www.esri.com/software/arcgis/.

Federal Emergency Management Agency, 2009, Flood insurance study, Johnson County, Kansas, and incorporated 

areas: Washington D.C., Flood Insurance Study Number 

20091CV001B.

Fry, J., Xian, G., Jin, S., Dewitz, J., Homer, C., Yang, L., 

Barnes, C., Herold, N., and Wickham, J., 2011, Completion 

of the 2006 national land cover database for the conterminous United States: Photogrammetric Engineering and 

Remote Sensing, vol. 77, no. 9, p. 858–864.

National Weather Service, 2014, Advanced Hydrologic Prediction Service: accessed August 5, 2014, at http:/water.

weather.gov/ahps/.

Omernik, 1987, Ecoregions of the conterminous United States: 

Association of American Geographers, v. 77, p. 118–125

U.S. Army Corps of Engineers, Hydrologic Engineering 

Center, 2009, HEC-GeoRAS, GIS tools for support of 

HEC–RAS using ArcGIS, user’s manual (v. 4.2): [variously 

paged]. 

U.S. Army Corps of Engineers, Hydrologic Engineering 

Center, 2010, HEC–RAS river analysis system, hydraulic 

reference manual (v. 4.1): [variously paged].

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accessed July 19, 2014, at http://www.census.gov/

popfinder/?fl=42:4204332800.

U.S. Geological Survey, 2014a, USGS surface-water data for 

the Nation: U.S. Geological Survey, accessed July 20, 2014, 

at http://waterdata.usgs.gov/nwis/sw.

U.S. Geological Survey, 2014b, USGS flood inundation mapping science: U.S. Geological Survey, accessed July 25, 

2014, at http://water.usgs.gov/osw/flood_inundation.

U.S. Geological Survey, 2014c, U.S. Geological Survey 

National Water Information System: accessed August 5, 

2014, at http://waterdata.usgs.gov/.

Whitehead, M.T., and Ostheimer, C.J., 2009, Development 

of a flood-warning system and flood inundation mapping 

for the Blanchard River in Findlay, Ohio: U.S. Geological 

Survey Scientific Investigations Report 2008–5234, 9 p.

Publishing support provided by: 

Rolla Publishing Service Center

For additional information concerning this publication, contact:

Director, USGS Kansas Water Science Center 

4821 Quail Crest Place

Lawrence, KS 66049

(785) 842–9909

Or visit the Kansas Water Science Center Web site at:

http://ks.water.usgs.gov

Studley and Peters—Flood-Inundation Maps for Indian Creek and Tomahawk Creek, Johnson County, Kansas, 2014—Scientific Investigations Report 2014–5202

ISSN: 2328-0328 (online) 

http://dx.doi.org/10.3133/sir20145202